This invention relates in general to the construction of tube couplings and in particular to a new and useful tube coupling for coupling together tubes and which includes an inner elastic lining permitting axial displacement of the coupled tubes within defined limits without breaking the sealing connection.
Tube couplings which are intended particularly for connecting large-size, glass fiber reinforced plastic tubes, such as laid underground, are known for example, from Swiss Pat. No. 600228 and have proved very satisfactory in service. The inside contour or profile of the sealing element provided with suitable protuberances and/or sealing lips usually comprise an axially short separating flange extending lengthwise in the middle and having an inside diameter corresponding to that of the tubes to be connected, and serving as a stop for the mostly bevelled front faces of the tubes.
Experience has shown that under certain loading conditions which, for example, tend to buckle the tubes at the joint or to push them together, the tubes or the connecting sleeve may break or the sealing element may be damaged and cause leaks. This particularly applies to displacements caused by tectonic earth motions or forces of similar effect. Especially in earthquake zones, underground jointed tubes may be exposed to forces which push them axially against each other and which cannot be absorbed by the elasticity of the tube or connecting sleeve nor by the static friction between the tube and the sealing element